It is imperative that individuals with physical impairments maintain an active lifestyle to enhance various aspects of well-being and overall quality of life. This population, however, are also one of the most sedentary in society. One identified reason for this is the ableism which exists in many fitness establishments that promotes acceptance of one particular body; the strong, physically athletic, muscular body is given value. Individuals who do not align to his particular physical reality may be subject to discrimination which can have a detrimental effect on their psycho-emotional well-being and deter them from exercising. Surprisingly, there is an increasing number of disabled individuals who are becoming gym instructors and further integrating themselves into a space which is deemed to oppress them. The purpose of this PhD is to explore these individuals' journey from gym clients to gym instructors. Framed by interpretivism and with particular focus on narrative inquiry, various qualitative analysis techniques were applied to explore 1) participants experiences exercising in the gym, 2) participants' motivations to be gym instructors, 3) how participants made sense of their gym instructor training and, 4)what impact participants perceived they had in the gym as instructors. This thesis has made original contributions to the literature by crafting a deep understanding of disabled people s experiences in the gym and why people enact social missions. For example, this thesis contextualizes disability in the gym and identifies that despite the numerous health benefits disabled people experience by exercising in this space, the psycho-emotional disablism they are subject to acts as a barrier for individuals to exercise here. Importantly, although disablism acted as a barrier to continued exercise for participants, it was also a facilitator in their decision to become a gym instructor. Essentially, participants described their own negative gym experiences as fuelling their desires to enact positive change in this space and do social missions in the gym. To be a gym instructor, participants went through a training programme specifically designed to train disabled people to embody this role. At this training, participants initially experienced a sense of validation and belonging through peer group exercise and were able to craft a collective story which allowed them to resist the oppressive disablism they experienced in the gym. However, as training continued and evolved so too did the narratives participants crafted to make sense of their experiences. Instead of one united story, participants crafted two conflicting narratives which redefined their relationship with each other and InstructAbility, and ultimately determined why some participants continued their training and others did not. For those who did continue to become fully qualified gym instructors, they felt they had a positive influence in promoting inclusion, exercise and diversity in the gym. In light of these findings, there are several practical recommendations for exercise practitioners, rehabilitation specialists, gym managers and those prescribing exercise to disabled people. Implications are aimed at improving exercise promotion and experiences of exercise in the gym for disabled people. For example, disabled gym instructors could be a way to bridge the perceived experiential gap between disability and the gym as they exhibit an alternate way of being which is accepted in this space. Through their experiential knowledge of disability and practical knowledge of exercise, these individuals can also relate to disabled clients in a way that non-disabled instructors cannot. Disabled gym instructors, however, can educate non-disabled gym instructors in how to train someone with an impairment. Equally, a more critical attitude to promoting exercise to disabled people is called for. Specifically, to steer away from disabling expectations and narratives of disabled people s motivations to exercise and move towards more realistic, enabling strategies and narratives to facilitate disabled peoples exercise behaviour.